Facebook CTO Bret Taylor, who once described himself as being in “violent agreement” with Mark Zuckerberg, is reportedly stepping down later this summer to work for an unnamed startup. Taylor has been a leading figure behind some of the most familiar innovations in the last decade – Google Maps, Facebook’s social plugins and Open Graph. His decision to abandon Facebook for a startup is an ominous sign for a company that, until its disappointing IPO, was considered an unstoppable juggernaut.

Taylor joined Google in 2003 and was the co-creator and project leader for the team that built Google Maps. He left in 2007 and created the social sharing site FriendFeed. Facebook bought the site in 2009 and hired Taylor. He was named CTO less than a year later.

While at Facebook, he oversaw platform and mobile, which included projects like the Graph API, Open Graph and App Center. Mike Vernal and Cory Ondreijka, who worked under Taylor, will take over platform and mobile, according to tech news site All Things D.